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Subatomic Particles

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Subatomic Particles

Atomic Number | Isotopes | Ions

Learning Objectives

- Understand the importance of atomic numbers
- Find the numbers of subatomic particles in a given isotope
- Calculate the average atomic mass of an element using isotopic composition
- Determine the charge of an ion based on numbers of subatomic particles

- Subatomic Particles

- Neutrons
- Neutral charge, 0
- 1 amu

- Protons
- Positive charge, +1
- 1 amu

- Atomic number– the number of protons in an atom, which determines the identity of an element
- Modern periodic table is arranged by atomic number
- Ex) All atoms containing 6 protons are carbon atoms

- Modern periodic table is arranged by atomic number

- Atomic Number

- Isotopes – the atoms of the same element that contain different numbers of neutrons and therefore have differing masses
- Mass number – the sum of the number of neutrons and the number of protons in an isotope

- Isotopes

- Isotopic notation
- Mass number written as a superscript in front of the element’s symbol
- Atomic number written as a subscript in front of the element’s symbol

- Isotopes

- Finding the Number of a Subatomic Particle

Ex) How many neutrons does contain?

- Strategy
- Given and unknown
- Formula

- Conversions needed?
- Intermediates needed?
- Solve
- Does the result make sense?

- No.

No.

Yes.

so

- Value given for element’s mass on periodic table
- Isotopic composition– the relative amounts of each isotope of an element found in a sample
- Percent abundance– the percentages that describe isotopic compositions

- Average Atomic Mass

- Average atomic mass – the weighted average of the masses of all stable isotopes of an element
- Atomic mass unit (amu) – a unit of mass equal to one-twelfth the mass of a carbon-12 atom

- Average Atomic Mass

- Finding Average Atomic Mass

Step 1Change the given percent abundances into decimal form.

Step 2Multiply the given mass of each isotope by its percent abundance in decimal form.

Step 3Find the sum of these values.

- Finding Average Atomic Mass Example Step 1

Step 1Change the given percent abundances into decimal form.

Ex) Use the information in the data table to find the average atomic mass of silver.

- Finding Average Atomic Mass Example Step 2

Step 2Multiply the given mass of each isotope by its percent abundance in decimal form.

Ex) Use the information in the data table to find the average atomic mass of silver.

- Finding Average Atomic Mass Example Step 3

Step 3Find the sum of these values.

Does the result make sense?

Ex) Use the information in the data table to find the average atomic mass of silver.

Yes.

- Electrons
- Outside nucleus
- Negative charge, –1

- Atoms containing equal numbers of protons and electrons are neutrally charged
- Ion– an atom that has an overall charge because it does not contain the same number of protons and electrons
- Cation– a positively charged ion formed when an atom loses one or more electrons
- Anion–a negatively charged ion formed when an atom gains one or more electrons
- Charge equals sum of charges of protons and electrons

- Ions

- Finding the Charge of an Ion

Step 1Find the sign of the charge by determining whether protons outnumber electrons or electrons outnumber protons in the ion.

Step 2Find the magnitude of the charge by determining the difference between the number of protons and electrons in the ion.

- Finding the Charge of an Ion

Step 1Find the sign of the charge by determining whether protons outnumber electrons or electrons outnumber protons in the ion.

Electrons outnumber protons, so this is an anion. The ion will be negatively charged.

Step 2Find the magnitude of the charge by determining the difference between the number of protons and electrons in the ion.

There is one more electron than proton, so the magnitude of the charge is 1. The charge of the ion is –1.

Does the result make sense?

Ex) What is the charge on an ion that contains 53 protons and 54 electrons?

- Yes.

Learning Objectives

- Understand the importance of atomic numbers
- Find the numbers of subatomic particles in a given isotope
- Calculate the average atomic mass of an element using isotopic composition
- Determine the charge of an ion based on numbers of subatomic particles

- Subatomic Particles